Electronic time delay relay



1959 H. L. VON GUGELBERG 2,912,626

ELECTRONIC TIME DELAY RELAY Filed April 25, 1956 United States PatentELECTRONIC TIME DELAY RELAY Hans Luz von Gugelberg, Maienfeld,Switzerland Application April 25, 1956, Serial No. 580,500

Claims priority, application Switzerland June 20, 1955 8 Claims. (Cl.317-142) This invention relates to an electronic time delay relay whichcomprises a condenser whose change of charge determines the delayedaction of the time delay relay, a source of direct current voltage forcharging said condenser, and an electronic discharge tube having acontrol element which induces the tripping action of the time delayrelay when the charge of said condenser reaches a definite value.

Objects of the invention are to provide, in an electronic time delayrelay of the type stated, an ionization chamber for changing the chargeof said condenser, a source of radioactive radiation disposed to emitprodnets of radioactive decay into the discharge space of saidionization chamber, and mechanically controllable means for controllingthe quantity of the products of radioactive decay that penetrate intothe discharge space of said ionization chamber, whereby the delayedaction of the time delay relay can be adjusted to a desired value. Yetanother object of the invention is an electronic time delay relay of thekind outlined, wherein said condenser is connected between the coldcathode and the starter electrode of a glow discharge tube, saidionization chamber is connected between said starter electrode and thepositive pole of a source of direct current voltage provided to chargesaid condenser, and a current limiting resistor is provided throughwhich the main discharge circuit of said glow discharge tube is fed fromsaid source of direct current voltage.

These and other objects and the advantages of the invention will best beunderstood from the following description of specific embodiments whenread in connection with the accompanying drawing in which:

Fig. 1 shows a simplified diagram explaining the principle of the modeof operation of the electronic time delay relay, and

Fig. 2 shows a modification of the means for controlling the quantity ofthe products of radioactive decay that enter the ionization chamber.

The electronic time delay relay shown in Fig. 1 is fed directly from theA.C. supply means through the terminals 1. The metal rectifier elements2 provide the direct current of 200 to 300 volts required for theoperation of the device, the D.C. current being adequately smoothed by acondenser 3 having a capacity of only a few microfarads. The positivepole of the D.C. voltage thus obtained is connected to one contact of aswitch 4 by means of which the relay can be put into operation at will.For reasons that will be hereinafter explained a glow discharge tube 5is provided comprising an anode 6, a cold cathode 7 and a starterelectrode 8. The anode 6 is joined to the second contact of the switch 4through the energizing coil 9 of an electro-mechanical relay. The latteris provided with two well insulated pairs of contacts 10 and 11 whichare open when the winding 9 carries no current. The energizing coil 9also serves as a resistance to limit the current and when .used inconjunction with the normal type of cold cathode tube 5 its ohmicresistance is a few thousand ohms. The

2,912,626 Patented Nov. 10, 1959 ice pair of contacts 11 across theterminals 12 can complete the external load circuit which is to beopened or to be closed at the end of the desired delay period. The othercontacts 10 serve to discharge the condenser 13 through the ohmicresistance 14, which has a value of a few hundred ohms, as soon as theglow discharge tube 5 fires and the external load circuit has beenclosed. The condenser 13 whose change of charge determines the delayperiod is located between the starter electrode 8 and the cold cathode 7of the glow dis charge tube 5. The change in charge of this condenser 13takes place through an ionization chamber, one electrode 16 of which isconnected to the starter electrode 8 whereas the other electrode 15 isconnected to the main switch 4. The electrodes 15 and 16 consist of twometal plates of suitable shape and of a few square centimetressuperficial area, well insulated the one from the other, and exposed tothe free atmosphere. The mean distance between the two plates 15 and 16may be between one and five centimetres. This ionization chamberreplaces the normally used variable ohmic resistance through which thecondenser 13 is gradually charged.

To render the space between the plate electrodes 15 and 16 conductivefor the discharge of an electric current, a source of radioactiveradiation 17 is arranged in close proximity thereto. This emits chieflyalphaparticles (helium nuclei with two elementary positive charges) intothe discharge space between the plates 15 and 16. Preferably the sourceof radioactive radiation is a preparation containing plutonium, radium,or actinium attached to an arm 18 made of metal or an insulatingmaterial and facing the discharge space. Plutonium, radium, or actiniumare suitable radioactive materials for the purpose in question becausetheir half-value period is sufiiciently long and the alphaparticlesemitted have only a limited range of not more than a few centimeters inair at atmospheric pressure. The degree of ionization in the dischargespace can be controlled by simple means. As shown in Fig. l the arm 18may be mounted on a rotatable spindle 19 which allows the distance ofthe source of radioactive radiation 17 from the discharge space to bevaried. Owing to the limited range of the alpha-particles ionization ofthe air space between the plates 15 and 16 becomes less as theradioactive preparation 17 is swung further away.

An alternative form of construction for controlling the number ofalpha-particles emitted by the radioactive source 17 that penetrate intothe space between the two electrodes 15 and 16 is shown in Fig. 2. Thisarrangement differs from the one previously described with reference toFig. 1 inasmuch as the source of radioactive radiation 17 is mounted ona bracket 18 which is fixed in relation to the plate electrodes 15 and16. However, a profiled disc 20 is mounted on a rotatable shaft 19 insuch manner that it can be interposed to a greater or lesser extent, atwill, between the radioactive source and the plates 15, 16. Since thealpha-particles emitted by plutonium, radium, or actinium have toolittle energy to penetrate deeply into solids the profiled disc acts asa shutter by means of which the discharge space of the ionizationchamber can be controllably screened from the rays of the radioactivepreparation 17. The more the radiation from the source 17 is cut off thesmaller will be the degree of ionization of the air in the space betweenthe plates 15, 16. The shaft 19 may be provided with a control knob forturning the shaft 19 with reference to a calibrated scale. By giving thedisc 20 a suitable profile any desired functional relation between thesubdivisions of the scale and the degree of ionisation can beestablished.

When the switch 4 (Fig. 1) is closed the plate electrode 15 will assumethe full positive D.C. voltage dealpha-particles thatreach theionisation chamber.

livered by the rectifier elements 2. On the other hand, the plateelectrode 16' will"b'e"substantially at the same potential asthatof"thecath'ode 7 since'the capacity of the condenser 13 of say 10,000lL/Lf. is substantially greater than the capacity between the two plateelectrodes .15 and lfifwhicli' may'teer the order of onlya"f ew ,u Lf.The starterelec'trode"8 is therefore at nearly'the same potential asthe'cathode T'and the cond'ense'r13 will have practically no char e." Nodischarge "takesplacebetween theano'de 6 and the cathode'7 so that theenergizing 'c'oil 9' ofthe relay remains de energize'd and'th'e contactsand 11 remain open. "Owing to the pene- (ration of alpha-particlesemitted by the radioactive some 17 into the "discharge space between"the plate electrodes and 16the 'air between the" plates" will be ionizedand an" electric cirr'rent "will pass" between the v two platesand1h'caiisingthecondenser13'to re- 11 soas to complete the externalload circuit which is connected to the terminals 12. ,'At the same timethe contacts 10 close likewise and allows the condenser 13 to dischargerapidly through the resistor 1 The connections thus established will bemaintained so long as the switch4 remains closed. As soon as the switch4 is opened the main discharge through the glow discharge tube 5 willcease, the contacts 10 and11 open, and the position shown in Fig. 1 willbe 're-established, the time delay relay being ready for renewedoperation.

The time delay, that is to say the *time that elapses from the closingof switch 4 to the moment the glow discharge tube.5 fires, can be madeto be independent of any fluctuations in the voltage of'the AC. supplymeans. The starting voltage at whicha spark occurs betweeen the starterelectrode 8 and the cathode 7 does not in any way depend upon thepotential difference between the cathode 7 and the anode 6 in a glowdischarge tube. Moreover, the weak electric current that passesbetween'the plate electrodes 15 and 16 of the ionization chamber can bemade to be entirely'independentof fluctuations in the DC supply voltageby operating the ionization chamber within the saturation range ofitscurrent-voltage-characteristic. To ensure-that this is so the potentialdifference between the-plate electrodes 15 and 16 need only'bemaintained ata saturation value during the whole period'that thecondenser 13 is being charged. Assuming that the potential differencebetween the plate electrodes 15 and 16 exceeds 150 volts, at a meandistance between the plate electrodes '15 and 16 of about one-to twocentimetres, the current flow will be substantially the saturationcurrent which does not depend upon the applied voltagebut'only upon'theposition of the shaft 1% which-controls the number of Once the'positionof the shaft 19 has been set the electrical discharge between the-plates15 and 16 will be maintained at a'constant level and the voltageacrossthe condenser 13 will increase proportionally-to theelapse oftime. The proportionality factor of this rise of potential can beadjusted to any desired value by means of the shaft 19 whose angularposition can be indicated by a scale which can be directly calibrated inunits'or" time delay. 1 i

By'giving the electrodes 15 and 1-6 a suitable shape becomeswithincerta'in'limits practically"independent 0f 5. The" invention asrecited in'claim 1, wherein active decay into said ionization chamber.

variations in atmospheric temperature and pressure. To satisfy thisrequirement the electrodes which enclose theionizationspacemaybe-curvedordisposed at an angle relative to each otherinstead of being embodied in fiat parallel plates.

According to the activity of the source of radioactive radiation 17 theelectrical discharge current between the electrodes 15 and 16 may be ofthe order 10-' to 1 0 amperes. Currents of this magnitude will charge acondenser 13 of-"10,000 [.L/Lf. to volts in the course of 10 to 10seconds. It follows that the electronic time delay relay according totheinvention 'hereinbefore described is'capable'of giving delays rangingbetween a few seconds to over a day although its action relies uponan"extremely"cheap' and small'condenser 13. Shorter delays can bereadily obtained simply by using a condenser 13 of even smallercapacity. However, the electrical components which primarily control theelectronic delay action must have the required high leakageresistancewhich according to the'time delay that may be desired shouldrange between 10 and 10 ohms. This applies more particularly to thecontrol'e'lement 8 of the valve 5. Moreovenif the minimum power outputdelivered by the valve 5 to the'windi'ng 9 of. the electromechanicalrelay is required to be at least one hundred milliwatts the necessaryhigh leakage resistance can only be obtained by using a glow dischargetube witha cold cathode 7 and a starter electrode 8. Hotcathode valvesfail because either their operating voltages are too low or becausetheir grid leakage currents are too high.

The invention is not limited to the particular embodiment's here shownand described. Various modifications maybe made in the electronic delayrelay withoutdeparting from the spirit and scope of the invention'as setforth in the following claims.

'I claim: o

1; An electronic time delay relay for closing relay contacts in anelectric circuit comprising a source of direct current, an energizingcoil connected in series with said current source for closing the relaycontacts, an electronic discharge tube connected in series with saidenergizing coil, said tube having a control element, condenser meansconnected to said control element to cause said tube to be conductivewhen the charge on said condenser means reaches a predetermined value,an ionization chamber having spaced electrodes connected in series withsaid condenser means,-a source of radioactive radiation adjacent saidionization chamber I for emitting products of radioactive decay withinsaid chamber to develop a progressively increasing charge onsaidcondenser, and mechanically adjustable means for controlling thequantity of the products of radioactive decay that penetrate into saidionization chamber so that the delayed action of the time delay relaycan be adjustedto adesired value.

2. An electronic time delay relay as defined in claim 1 wherein saidcondenser means has a capacity on the order of 10,000 ref.

3. The invention as recited in claim 1, wherein said mechanicallyadjustable means comprise a shutter movably disposed between said sourceof radioactive radiation and said ionization chamber.

- 4. The invention as recited in claim 1, wherein said mechanicallyadjustable meanscomprise an arm which can be moved with respect to thedischarge space of said ionization chamber, and said sourceofradioactive radiation is attached to said movable arm. 7 4

said source of radioactive radiation contains radioactive materialswhich emit alpha-particles as products of radio- *6. An electronic timedelay relay for closing relay contacts in'an electric circuit comprisinga source of direct current; an'energizing coil'connected in series withcurrent source for closing the relay contacts," a glow discharge tubeconnected in series with said energizing coil, said tube having a coldcathode, an anode and a starter electrode, a condenser connected betweensaid cold cathode and said starter electrode to cause said tube to firewhen the charge on said condenser reaches a predetermined value, anionization chamber having a pair of electrodes, one of said ionizationchamber electrodes being connected to said starter electrode and theother chamber electrode being connected to a positive terminal of saiddirect current source, a source of radioactive radiation adjacent saidionization chamber for emitting products of radioactive decay withinsaid chamber to develop a progressively increasing charge on saidcondenser, and mechanically adjustable means for controlling thequantity of the products of radioactive decay that penetrate into saidionization chamber so that the delayed action of the time delay relaycan be adjusted to a desired value.

7. An electronic time delay relay as defined in claim 6 wherein saidenergizing coil functions as a current limiting resistor through whichthe main discharge circuit of said glow discharge tube is fed from saiddirect current source, and further including means for discharging saidcondenser upon the firing of said glow discharge tube.

8. An electronic time delay relay as defined in claim 7 wherein thegeometric dimensions of the ionization chamber are chosen so as to causesaid chamber to operate within the saturation range of itscurrent-voltage characteristic.

References Cited in the file of this patent UNITED STATES PATENTS2,360,721 Rose Oct. 17, 1944 2,549,058 Constable Apr. 17, 1951 2,567,928Farmer Sept. 18, 1951 2,596,956 Nierman May 13, 1952 2,606,296 SimpsonAug. 5, 1952 2,615,063 Brown Oct. 21, 1952 2,760,080 Robinson Aug. 21,1956 2,783,388 Wintermute Feb. 6, 1957 FOREIGN PATENTS 960,955 FranceApr. 28, 1950

